For a mobile telephone system network which is commonly applicable to fixed communication and mobile communication, in the 3GPP (3rd Generation Partnership Project), a W-CDMA (Wideband Code Division Multiple Access) scheme has been standardized as a 3rd Generation cellular mobile communication scheme, and the services have been sequentially started. Moreover, HSDPA (High Speed Downlink Packet Access) with further increased communication speed has also been standardized, and the services are being started. Furthermore, in the 3GPP, Evolved Universal Terrestrial Radio Access (hereinafter referred to as “EUTRA”) has been studied.
As a downlink of the EUTRA, an OFDM (Orthogonal Frequency Division Multiplexing) scheme has been proposed. As an EUTRA technique, a technique such as an adaptive modulation and demodulation/error correction scheme (AMCS: Adaptive Modulation and Coding Scheme) based on adaptive radio link control (Link Adaptiveion) for channel coding and the like has been applied to the OFDM scheme. The AMCS scheme is a scheme for switching radio transmission parameters, such as an error correction scheme, an error correction coding rate, a data modulation multi-valued number (MCS: Modulation and Coding Scheme), a code Spreading Factor (SF) of time/frequency axes, and a multi-code multiplexing number, depending on a propagation path status at each mobile station, in order to efficiently perform high-speed packet data transmission. For example, for data modulation, a maximum throughput of a communication system can be increased by switching the modulation from QPSK (Quadrature Phase Shift Keying) modulation to more efficient multilevel modulation, such as 16QAM (Quadrature Amplitude Modulation) modulation or 64QAM modulation; as the propagation path status is improved. On the other hand, as an uplink of the EUTRA, a DFT-S-OFDM (Discrete Fourier transform Spread OFDM) scheme has been proposed (see the following Non-Patent Document 1).
FIG. 1 is a diagram showing a channel configuration in the EUTRA. The downlink of the EUTRA includes a Downlink Pilot Channel (DPiCH), a Physical Downlink Synchronization Channel (PSCH), a Physical Downlink Shared Channel (PDSCH), a Physical Downlink Control Channel (PDCCH), and a Physical Broadcast Channel (PBCH).
Moreover, the uplink of the EUTRA includes an Uplink Pilot Channel (UPiCH), a Random Access Channel (RACH), a Physical Uplink Shared Channel (PUSCH), and a Physical Uplink Control Channel (PUCCH) (for example, see the following Non-Patent Document 1).
Moreover, currently, in an argument related to the EUTRA, an MBMS (Multimedia Broadcast Multicast Service) service is studied. As a cell which provides the MBMS service, there are two cells including a cell (MBMS dedicated cell) which uses a frequency (a frequency dedicated to the MBMS service) which is different from a frequency used for unicast transmission and performs MBMS transmission in a dedicated manner, and a cell (MBMS/Unicast-mixed cell) which uses the frequency (a frequency which is not dedicated to the MBMS service) used for the unicast transmission and performs both the MBMS transmission and the unicast transmission. Any cell of them can be used to simultaneously provide the MBMS service to a plurality of users.
In addition, as an MBMS service transmission method, there are a method in which only one base station performs the transmission, and a method in which a plurality of base stations in time/frequency synchronization simultaneously perform the transmission. The former is referred to as “SCPTM (Single-Cell Point-to-Multipoint) transmission”, and the latter is referred to as “MBSFN (Multimedia Broadcast multicast service Single Frequency Network) transmission”. In the MBSFN transmission, the same MBMS transmission signals are simultaneously transmitted from the plurality of base stations, and the signals can be synthesized so that the signals can be seen as one MBMS transmission signal, in the mobile station. In this description, for convenience of explanation, a cell which performs the SCPTM transmission is referred to as “SCPTM cell”.
FIG. 2 is a diagram showing a schematic configuration example of the MBMS service in the SCPTM transmission. The same AMCS as the unicast transmission is applied to the MBMS transmission signal in the SCPTM transmission. As shown in FIG. 2, in a cell 23 which provides the MBMS service via the SCPTM transmission, a state where a plurality of mobile stations 20c, 20d and the like are receiving the MBMS service will be considered. It is assumed that a base station 10c which provides the MBMS service via the SCPTM transmission, and the two mobile stations 20c and 20d are included, and the mobile stations 20c and 20d are receiving the MBMS service.
It is assumed that, when a mobile station in an idle mode, which hopes to receive the MBMS service via the SCPTM transmission, is designated by the base station 10c based on the current specification described in the following Non-Patent Document 1, the mobile station transits from the idle mode to a connected mode, and is assigned with an uplink feedback resource, and periodically provides feedback. The mobile station in the connected mode, which has been assigned with the feedback resource for the MBMS, uses the feedback resource designated by the base station, to provide the feedback to the base station. This feedback information includes a Channel Quality Indicator (CQI, also referred to as “downlink channel quality information” or “CQI feedback information”) indicating downlink channel quality for each frequency domain, and ACK (Positive Acknowledgement)/NACK (Negative Acknowledgement) of HARQ (Hybrid Automatic Repeat Request) for data of the MBMS service. Particularly, if more detailed CQI feedback is further required, information indicating a frequency domain with good channel quality is fed back from the mobile station to the base station.
In FIG. 2, as shown by an arrow, for example, the mobile station 20c with poor downlink channel quality is providing the feedback. Based on the feedback information from the mobile station 20c, the base station 10c decides an MCS value (for example, 16QAM modulation, a ⅔ coding rate) which is a combination of the modulation multi-valued number and the coding rate in the AMCS, so that all the mobile stations 20c and 20d can receive the MBMS service, applies the MCS value to transmitted data of the MBMS service, and then performs the SCPTM transmission. It should be noted that the mobile station 20c which is providing the feedback is in the connected mode, and the mobile station 20d which is not providing the feedback is in the idle mode or the connected mode.    Non-Patent Document 1: 3GPP TS (Technical Specification) 36.300 V8.2.0 (2007-09), Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage2 (Release 8).    Non-Patent Document 2: 3GPP TS (Technical Specification) 36.304 V8.0.0 (2007-12), Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE) procedure in idle mode (Release 8).